Question

In acidic solution. A 70.0 mL sample of a solution containing Fe2+ requires 70.0 mL of a 0.150 M KMnO4 solution for complete reaction. What is the concentration of the Fe2+ in the original solution?

Answer 1

Answer:

0.75M Fe²⁺

Explanation:

First, we need to balance the redox reaction in acidic medium. Then, we can obtain moles of KMnO4 and with the reaction moles and molarity of the Fe²⁺ solution:

Redox Balance:

Fe²⁺ → Fe³⁺ + 1e⁻

5e⁻ + 8H⁺ + MnO₄⁻ → Mn²⁺ + 4H₂O

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5Fe²⁺ + 5e⁻ + 8H⁺ + MnO₄⁻ → 5Fe³⁺ + 5e⁻ + Mn²⁺ + 4H₂O

5Fe²⁺ + 8H⁺ + MnO₄⁻ → 5Fe³⁺ + Mn²⁺ + 4H₂O

Moles of KMnO₄:

70.0mL = 0.0700L * (0.150mol / L) = 0.0105 moles KMnO₄

Moles and molarity Fe²⁺:

0.0105 moles KMnO₄ * (5 moles Fe²⁺ / 1mol KMnO₄) = 0.0525 moles Fe²⁺

In 70.0mL = 0.0700L:

0.0525 moles Fe²⁺ / 0.0700L =

0.75M Fe²⁺